Your Sky Help: Asteroid and Comet Tracking

You can plot the orbit and current position of an asteroid (minor
planet) or comet by pasting its orbital elements into the text box
provided for that purpose. The orbital elements, which permit
calculation of the position of the object for a period of time
surrounding the Epoch for which they are computed, are entered in the form
currently published in the International
Astronomical Union (IAU) and Minor Planet Electronic
Circulars. Further information on
these electronic publications, including subscription information, is
given at the bottom of this page.

Asteroids

The first line in the text box is the name or provisional designation
of the object, and the lines that follow are the orbital elements
published in the Circular concerning it. If your
system supports cut-and-paste, you can copy the elements directly from
the E-mail Circular and paste them into the
elements box.

For example, here are the elements published in MPEC 1995-C12 of
February 6th, 1995 announcing the discovery of “1995 CR”, a new
extremely rare “Aten-type” asteroid which orbits the Sun in less
time than the Earth. 1995 CR, discovered on February 3, 1995 by R.
Jedicke with the 0.9 metre
Spacewatch
telescope at
Steward Observatory
on Kitt Peak,
crosses the orbits of all four inner planets. Press the
“Update” button below the elements to plot this asteroid's position at
the time of its discovery.

Orbital elements for asteroid or comet: Echo elements

On February 22, 1995, 1995 CR passed within 0.05 astronomical units of
the Earth, about 7.5 million kilometers: about 20 times the distance
of the Moon. Note that we checked the “Echo elements” box above.
This causes Your Sky to show the elements it obtained from
the text box immediately below the box, explaining what each value
means. Press “Update” again, then scroll down to see the echoed
elements, if you're interested.

Recovered Asteroids and Revised Elements

Elements for recovered asteroids (those re-observed after their
original discovery at a subsequent favourable apparition) and revised
elements based upon refinement of an orbit by subsequent observations
are published in a slightly different form, with an “Id.” line between
the object's name and the epoch of the elements. Your Sky
accepts this form as a well.

Here are revised elements for “1994 ES2”, a transneptunian object
which orbits entirely outside the orbits of Neptune and Pluto with an
orbital period of more than 311 years. These revised elements were
issued in MPEC 1995-E04 of March 1, 1995 which arrived as I was
writing the paragraphs above.

I've pasted the elements into the box below; press the “Update” below
it to see the path of this far-flung wanderer through the darkness.
I've set the time and date
to the time of the most recent observation cited in the
Circular,
and the observing site to the latitude
and longitude of Mauna Kea,
Hawaii, in the United States, where the
2.2 metre
University of
Hawaii reflector was used to spot this 24th
magnitude object.

Consulting the last line of the ephemeris, we
note that at the time of the observation, 1994 ES2 shone (if I may dare
to speak of a 24th magnitude object shining!) at an altitude of more than 72░
degrees in the pellucid skies with which Mauna Kea is blessed.

Comets

Orbital elements for newly discovered and recovered comets are
reported in the IAU Circulars. The format in which the elements are
given depends upon whether the comet is periodic (has a closed orbit
around the sun) or parabolic (a comet which appears from deep space
and leaves the solar system for good after its turn around the Sun, or
has such a long period that its trajectory isn't measurably different
from parabolic).

Periodic Comets

Elements for periodic comets are (usually) published in the following
form, this example taken from IAU Circular No. 6037 of July 25,
1994, reporting the first reliable orbit determination for comet
McNaught-Hartley (1994n), discovered on July 6, 1994 by
M. Hartley with the 1.2 metre
UK Schmidt
telescope at
Siding Spring,
Australia.

Click the “Update” button above to see this comet from the
viewpoint of the telescope which discovered it.

While the IAU Circulars publish orbital elements for periodic comets
in the form given above, the Minor Planet Electronic Circulars report
elements of comets in the same form they use for asteroids, except the
“M” entry for mean anomaly is replaced by a “T” entry giving perihelion
date. MPEC 1995-C11, issued on February 3, 1995 reported the
following elements for periodic comet P/1989 T2 (Helin-Roman-Alu 1)
as follows:

Your Sky detects these “stealth periodic comets” and handles
them correctly, as a click on the “Update” button above will
demonstrate.

Parabolic Comets

Click the button to see this comet as it appeared in late 1994 while
making its hairpin turn around the sun, before being “last seen
heading southbound on the interstellar”.

Note that elements for parabolic comets are in essentially the same
form as those for (most) periodic comets, with eccentricity omitted
(since it's always 1.0), and the semimajor axis, mean motion, and
period dropped since they're meaningless for a parabolic trajectory.

The IAU
Circulars, published by the
Central
Bureau for Astronomical Telegrams,
provide a means for distributing time-sensitive
information to observers. The Circulars announce novŠ and supernovŠ,
radio and X-ray transients, newly-discovered and recovered comets.
Companion Minor
Planet Electronic Circulars,
published by the
Minor Planet Center,
report asteroid
discoveries and related information. IAU Circulars used to be
delivered by telegram or post, but are now distributed by
electronic mail. A subscription costs US$6.00 per month, and includes
E-mail delivery of Circulars as they are published, and log-in
privileges to a machine with an archive of Circulars as well as
asteroidal orbital elements from the Minor Planet Center.
You can
subscribe to the
circulars by
sending a check (In US$) payable to the “Central Bureau for
Astronomical Telegrams” to: